Creating a pipeline, whether horizontally or vertically, and whether underground or above ground, one typically assembles consecutive lengths of pipe one after the other. Often, pipelines are formed by driving a first section of pipe axially into position, fixing a second length of pipe to the first, driving the joined first and second sections of pipe axially into position, adding a third length, and so on. Two examples of such pipeline formation may include auger boring and micro tunneling.
Traditionally, individual lengths of pipe used in forming a pipeline are arranged in a line, end-to-end, with each being welded to the next as individual lengths of pipe are added to the pipeline. However, welding the individual lengths of pipe to one another is a time-consuming process involving additional danger, high heat, skilled welding personnel, time to allow welds to cool, and possible imperfections in the finished product.
Press-fitting pipes together, where a first pipe with a male end is joined to a second pipe with a female end, is a possible alternative to welding. However, press-fitting lengths of pipe together creates additional challenges, including the great forces/pressures that are required to cause pipes, which may be made of steel or other metals, to deform enough to engage one another in a press-fit fashion. Additionally, press-fitting lengths of pipe to one another using currently-available press-fittings requires precise alignment of the pipes. Where two pipes are not perfectly aligned when pressure is applied to press-fit them together, the pipes may “buck” (that is, bend relative to one another at the union point) which may damage the pipes and/or equipment used to handle and join the pipes.
Furthermore, depending upon the application of the pipeline, the press-fit unions of lengths of pipes have to undergo great forces without separating or failing. Particularly, where pipelines are oriented horizontally, the lengths of pipes and thus the unions between the pipes, experience great compressive stresses during installation. Where pipelines are oriented vertically, the lengths of pipes and thus the unions between the pipes experience both compressive stresses as well as bending stresses. Thus, it is important that once lengths of pipe are press-fit together, they are not capable of being separated without destruction of one or both.
Accordingly, what is needed is a press-fit pipe connection that requires less force/pressure to join corresponding lengths of pipe, while being able to withstand the compressive and bending stresses that the pipes will experience both during installation and operation in the field.